The Wireless Energy Monitor consists of several sensors with a transmitter and a receiver. The transmitter and the sensors are placed in the meter cabinet next to the electricity meter and gas meter. You can use the doorbell transformer to power the transmitter. Thanks to the wireless link, the receiver can be used anywhere in the house to show your current power consumption on a LCD screen. You can thus use it in every room to see the effect on energy consumption of switching something on or off. The receiver is powered by a 9-V battery.